A conventional hearing aid or listening device includes a microphone that receives acoustic sound waves and converts the acoustic sound waves to an audio (frequency) (electrical) signal. That “audio signal” is then processed (e.g., amplified) and sent to the receiver of the hearing aid or listening device. The receiver then converts the processed signal to a corresponding acoustic signal that is broadcast toward the eardrum.
A conventional hearing aid or listening device can include both a microphone and a telecoil for receiving inputs. The telecoil picks up electromagnetic (broadcast) signals. The telecoil produces a signal voltage across its terminals when placed within an electromagnetic field, which is created by an alternating current of an audio frequency electromagnetic signal moving through a wire. The signal in the telecoil is then processed (e.g. amplified) and sent to the transducer (or receiver) of the hearing aid for conversion to a corresponding acoustic signal.
A typical “hearing aid” comprises a combination of a receiver and a microphone in one housing or “case.” The signal from the microphone to the receiver is amplified before the receiver broadcasts the acoustic signal toward the eardrum.
In a typical balanced armature receiver, the housing or “case” is made of a soft magnetic material, such as a nickel-iron alloy. The case serves several functions: firstly, its housing provides some level of sturdiness; secondly, it provides a structure for supporting the components and their electrical connections. Thirdly, the case provides both magnetic and electrical shielding. Lastly, the case may provide acoustical and vibrational isolation to the other parts of the hearing aid.
The broadcasting of the acoustic signal causes the receiver to vibrate. The vibrations can affect the overall performance of the listening device. For example, the vibrations in the receiver can be transmitted back to the microphone, causing unwanted feedback. Furthermore, in a hearing aid with a telecoil, a magnetic feedback signal may create feedback problems. Consequently, it is desirable to reduce the amount of vibrations and/or magnetic feedback that occur in the receiver of the hearing aid or listening device.
Presently available moving armature transducers have a minimum thickness, based upon the usual manner of assembly of the various parts. Typical such transducers/receivers are shown in FIGS. 1 and 2. While the receivers 10 and 10a shown in FIGS. 1 and 2 are essentially of the same configuration, they differ primarily in the design of the armature, FIG. 1 illustrating a so-called E-type armature 12, and FIG. 2 showing a U-type armature 12a. Accordingly, like reference numerals with the suffix “a” are used to designate the like parts and components of the receiver of FIG. 2, whereby the components of the receiver of FIG. 10 will be described in detail, it being understood that the components of the receiver of 10a of FIG. 2 are essentially the same.
A housing surrounds the working components of the receiver 10 and includes a case 14 and a cover 15. One end of the housing includes an output port 16 for transmitting the acoustical signal toward the users eardrum. An opposite end of the housing may include an electrical connector assembly 18 which may include provisions for various types of contacts or electrical connections such as by soldering or the like. This connector 18 receives an input audio frequency electrical signal that is converted by the internal working components of the receiver to an output acoustic signal (sound waves) which is broadcast from the output port 16.
The working components of the transducer or receiver 10 include a motor 20 which includes a magnet assembly 22 and a coil 24 which are coaxially located and in side-by-side abutting alignment. Through an axial center of the coil 24 and magnet assembly 22 is a moveable armature 12, which is moved in response to the electromagnetic forces produced by the magnet assembly 22 and coil 24 in response to the applied audio frequency electrical signal at the terminal 18. Thus, the corresponding motion of the armature 12 may be translated into acoustic energy (sound waves) by a diaphragm 30 which is mounted in the case 14 above the magnet assembly 22 and coil 24 and is operatively coupled with the armature 12 by a drive pin 32.
The overall thickness of the receiver 10 is defined by the thickness of the walls of the case 14 and cover 15, the thickness of the magnet assembly 22, which includes a magnet 26 and a magnet housing 28 surrounding the magnet 26, the diaphragm 30 and sufficient free airspace to permit vibration of the diaphragm to create acoustic energy or sound waves in response to the operation of the motor 20 as described above.
In hearing aids, it is generally desirable to decrease overall size of components where possible, and in particular, for hearing aides such as a behind the ear (BTE) hearing aid 40 (see FIG. 3) or “in the ear” (ITE) hearing aid (not shown). The overall width of the hearing aid is essentially determined by the thickness of the receiver.
In the U-type armature, receiver 10a of FIG. 2, an additional element to the overall thickness to the receiver is the second arm of the U-shaped armature 12a as indicated at reference numeral 12b. 